Michael Stone may yet not face a retrial. The fresh hearing ordered by the Court of Appeal yesterday will go ahead only if the new trial judge decides at the time that a fair hearing is still possible.

There were more than four hours of legal submissions yesterday over whether the nature of the publicity that followed Mr Stone’s original conviction would prevent him receiving a fair retrial.

William Clegg, QC, for the appellant, said: “Michael Stone can’t now receive a fair trial, such has been the wealth of prejudicial material adverse to him and inadmissible in any criminal trial.

“No jury could try his case fairly, and any conviction resulting would inevitably be unsafe.”

Mr Nigel Sweeney, QC, for the Crown, said: “We invest juries who try cases with good sense, good judgment and an ability within the trial to put out of their minds anything they might have heard before.”

The man accused of the murder of Lin Russell and her daughter Megan, and the attempted murder of Josie Russell, was told that the guilty verdicts at his trial in October 1998 were now considered to be unsafe. Argument by his defence team that he should be freed were rejected by the court.

Lord Justice Kennedy, sitting with Mrs Justice Hallet and Mr Justice Kay, said that they would give their reasons for overturning the conviction, and for not releasing Mr Stone, at a hearing to be held next week.

Mr Stone, 40, was accused of battering to death Mrs Russell, 45, and Megan, 6, as they walked along a country lane near Chillenden, Kent, on their way home from primary school in July 1996. Josie, then aged nine, was left for dead but has since made some recovery.

Mr Stone, unemployed, from Gillingham, Kent, was convicted after a trial at Maidstone Crown Court and given three life sentences. His retrial is expected to take place at the Old Bailey in the summer.

Mr Stone, a pale and stocky figure in a white polo shirt and dark trousers gazed around a packed courtroom on the second day of his appeal. He will remain in custody until his trial. If the trial judge believes that media publicity surrounding the high-profile case jeopardises the chances of a fair trial, then Mr Stone will be freed.

His sister Barbara, speaking on the steps of the High Court in London, said: “Michael Stone is very pleased that his convictions have been quashed and is looking forward to prove his innocence at the retrial.

“As the case is now sub judice, we will make no further comment.”

Josie’s father, Dr Shaun Russell, was informed of the court’s decision by a Kent Police officer who has been staying at the family’s new home in the Nantlle Valley, Gwynedd.

The Court of Appeal uses the yardstick of the “interests of justice” in considering whether to order retrials.

Before the Criminal Appeal Act 1988, it could order a retrial only on the basis of "fresh evidence" presented at the appeal. This was widely criticised as “too restrictive” in a series of cases which later turned out to be miscarriages of justice.

The 1988 Act broadened the test so that a retrial can be ordered “where it appears to the court that the interests of justice so require”.

Appeal judges take account of factors such as the gravity of the charge, the evidence and also the length of time since the offence.

They may order a retrial for the same offence which they have already quashed, another offence on the indictment or an offence which was put as alternative but which the jury did not have to reach a verdict on because of the conviction.

Retrials may be ordered despite the rule that offenders cannot be tried twice for the same offence. That rule, known as the “double jeopardy” principle, applies only where an offender has been acquitted and not where he has been convicted.

The rule is currently under review by the Law Commission, the law reform body for England and Wales, which is expected soon to recommend a relaxation under strictly defined circumstances.

The Government is expected to back such proposals which are also supported by the Conservatives. In cases of murder, for instance, this could mean that an offender could be tried a second time if compelling new evidence - such as DNA material - came to light.

The Law Commission is also looking at stronger prosecution rights of appeal against a judge’s rulings that there is “no case to answer”.

Retrials can be and are regularly ordered by the Court of Appeal where the original conviction is not regarded as “safe”.

Sheila Bowler, a music teacher from Rye, Sussex, was finally cleared in 1998 of murdering her aunt. Juries are told to put out of their minds anything they may have read and consider only the evidence before them.

Equally the Court of Appeal has ruled the media publicity can prejudice the right to a fair trial.

In 1991, the court allowed an appeal against conviction by the two sisters, Michele and Lisa Taylor convicted of murdering Alison Shaughnessy, a bank clerk.